EDWARD'S LECTURE NOTES:
More notes at http://tanguay.info/learntracker
C O U R S E
Paleontology: Early Vertebrate Evolution
Alison Murray, University of Alberta
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C O U R S E L E C T U R E Diversity of Early Vertebrate Life Notes taken on July 23, 2019 by Edward Tanguay |
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as paleontologists look back into the past, the further they look, the blurrier and smaller the view finder becomes
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with living animals we can observe them directly
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with animals from the Paleozoic Era (542-250 Ma, fish) or Mesozoic Era (250-65 Ma, dinosaurs) we observe them through fossils
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becoming a fossil was like striking the lottery
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as some soft Paleozoic life form, the chances of your remains being preserved was exceptionally small
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and after a fossil was formed, it had to beat the odds again and again throughout the eons to survive until it was eventually be uncovered and studied
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there is about a half billion years between the first appearance of vertebrates in the fossil record and today
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during this time, sediments and their fossils were regularly destroyed
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localities of exceptional preservation are all the more valuable for what they can tell us
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we call these areas of exceptional preservation Lagerstätten
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a German word that means storage place
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it's only through specific Lagerstätten that we know anything about the earliest animals and vertebrates
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because these were animals that were all soft-bodied
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such localities are snapshots which afford us a brief glance of life at specific times of our Earth's history
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the first evidence of life that we have in the fossil record is that of microbes
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640 million years ago
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bacteria and other single-celled organisms dominated the earth from around 3.8 billion years ago to 640 million years ago
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life was mostly made up of microbial mass
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on a twelve hour clock of evolutionary scale, higher animals don't show up until about 10:00, only two hours of evolution
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before that it was only microbes
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Ediacaran Period (635-542 Ma)
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first multicellular life
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first appearance worldwide of somewhat complicated trace fossils
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Cambrian Period (542-485 Ma)
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rapid diversification of lifeforms known as the Cambrian explosion
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high proportion of Lagerstätte sedimentary deposits with exceptional preservation
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Burgess Shale biota (508 Ma, middle of Cambrian Period)
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soft-bodied organisms
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first appears over 600 million years ago
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first organisms to produce shells
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modern animals
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have anterior and posterior end
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dorsal and ventral
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bilateral
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bilateral animals like fish have heads, while radial animals like sea urchin don't
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bilateral animals move forward or backward
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radial animals more in any direction
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therefore for bilateral animals, sensory organs become concentrated at the anterior end
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most animals are bilaterally symmetrical
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exception are echinoderms, e.g. starfish
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some early fossiles are bilateral and are probably our ancestors
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Cambrian Explosion
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complex and multicellular life began to diversify in the Pre-Cambrian supereon
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increased heavily in the Cambrian period (after 542 Ma)
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increase in level of oxygen in oceans and atmosphere
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rising sea levels
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shallow water environment
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animals evolved hard parts
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enabled them to have protect themselves and rise up to the surface
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Burgess Shale
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shales deposited more than 500 million years ago
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cliffs of the reefs protected it when the Rocky Mountains formed
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animals lived in still water
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flattened impressions of the animals
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black color films made of iron-rich minerals
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traced the outline of the soft tissues
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closest relative of living vertebrates
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Metaspriggina
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two large eyes
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vertebrae-like structures in the back
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a large brain in front to process information from the eyes
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segmented muscle bundles
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-myomeres
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could weave their way through the water